This pair of calls allows plugins to describe which extents in the virtual disk are allocated, holes or zeroes. --- docs/nbdkit-filter.pod | 64 +++++++++++++++++++++ docs/nbdkit-plugin.pod | 123 ++++++++++++++++++++++++++++++++++++++++ include/nbdkit-common.h | 20 ++++++- include/nbdkit-filter.h | 15 ++++- include/nbdkit-plugin.h | 6 +- server/internal.h | 7 ++- server/extents.c | 71 +++++++++++++++++++++++ server/filters.c | 61 ++++++++++++++++++++ server/plugins.c | 62 +++++++++++++++++++- server/Makefile.am | 1 + 10 files changed, 425 insertions(+), 5 deletions(-) diff --git a/docs/nbdkit-filter.pod b/docs/nbdkit-filter.pod index dc9a262..6e81e0c 100644 --- a/docs/nbdkit-filter.pod +++ b/docs/nbdkit-filter.pod @@ -350,6 +350,8 @@ calls. =head2 C<.can_zero> +=head2 C<.can_extents> + =head2 C<.can_fua> =head2 C<.can_multi_conn> @@ -365,6 +367,8 @@ calls. void *handle); int (*can_zero) (struct nbdkit_next_ops *next_ops, void *nxdata, void *handle); + int (*can_extents) (struct nbdkit_next_ops *next_ops, void *nxdata, + void *handle); int (*can_fua) (struct nbdkit_next_ops *next_ops, void *nxdata, void *handle); int (*can_multi_conn) (struct nbdkit_next_ops *next_ops, void *nxdata, @@ -513,6 +517,66 @@ value to return to the client. The filter should never fail with C<EOPNOTSUPP> (while plugins have automatic fallback to C<.pwrite>, filters do not). +=head2 C<.extents> + + int (*extents) (struct nbdkit_next_ops *next_ops, void *nxdata, + void *handle, uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map, + int *err); + +This intercepts the plugin C<.extents> method and can be used to +modify extent requests. + +This function will not be called if C<.can_extents> returned false; in +turn, the filter should not call C<next_ops-E<gt>extents> if +C<next_ops-E<gt>can_extents> did not return true. + +The C<extents_map> parameter passed to this function is empty +(representing a fully allocated disk). If the filter does not need to +adjust extents from the underlying plugin it can simply pass this +through to the layer below: + + myfilter_extents (...) + { + return next_ops->extents (nxdata, count, offset, flags, + extents_map, err); + } + +It is also possible for filters to transform the extents map received +back from the layer below. Usually this must be done by allocating a +new, empty map which is passed to the layer below. Without error +handling it would look like this: + + myfilter_extents (...) + { + struct nbdkit_extents_map *map2 = nbdkit_extents_new (); + next_ops->extents (nxdata, count, offset, flags, map2, err); + /* transform map2 and return results in extents_map */ + nbdkit_extents_foreach (map2, transform_offset, extents_map); + nbdkit_extents_free (map2); + } + +If there is an error, C<.extents> should call C<nbdkit_error> with an +error message B<and> return -1 with C<err> set to the positive errno +value to return to the client. + +=head3 Allocating and freeing nbdkit_extents_map + +Two functions are provided to filters for allocating and freeing the +map: + + struct nbdkit_extents_map *nbdkit_extents_new (); + +Allocates and returns a new, empty extents map. The initial state is +that the whole disk is allocated with data. + +On error this function can return C<NULL>. In this case it calls +C<nbdkit_error> and/or C<nbdkit_set_error> as required. + + void nbdkit_extents_free (struct nbdkit_extents_map *); + +Frees an existing extents map. + =head1 ERROR HANDLING If there is an error in the filter itself, the filter should call diff --git a/docs/nbdkit-plugin.pod b/docs/nbdkit-plugin.pod index 47545f3..406019d 100644 --- a/docs/nbdkit-plugin.pod +++ b/docs/nbdkit-plugin.pod @@ -555,6 +555,20 @@ This callback is not required. If omitted, then nbdkit always tries C<.zero> first if it is present, and gracefully falls back to C<.pwrite> if C<.zero> was absent or failed with C<EOPNOTSUPP>. +=head2 C<.can_extents> + + int can_extents (void *handle); + +This is called during the option negotiation phase to find out if the +plugin supports detecting allocated (non-sparse) regions of the disk +with the C<.extents> callback. + +If there is an error, C<.can_extents> should call C<nbdkit_error> with +an error message and return C<-1>. + +This callback is not required. If omitted, then we return true iff a +C<.extents> callback has been defined. + =head2 C<.can_fua> int can_fua (void *handle); @@ -717,6 +731,115 @@ If there is an error, C<.zero> should call C<nbdkit_error> with an error message, and C<nbdkit_set_error> to record an appropriate error (unless C<errno> is sufficient), then return C<-1>. +=head2 C<.extents> + + int extents (void *handle, uint32_t count, uint64_t offset, + uint32_t flags, + struct nbdkit_extents_map *extents_map); + +During the data serving phase, this callback is used to detect +allocated, sparse and zeroed regions of the disk. + +This function will not be called if C<.can_extents> returned false. +nbdkit's default behaviour in this case is to treat the whole virtual +disk as if it was allocated. + +The callback should detect and return the list of extents overlapping +the range C<[offset...offset+count-1]>. The C<extents_map> parameter +points to an opaque object which the callback should fill in by +calling C<nbdkit_extent_add> etc. See L</Extents map> below. + +The C<flags> parameter may contain the flag C<NBDKIT_FLAG_REQ_ONE> +which means that the client is only requesting information about the +extent overlapping C<offset>. The plugin may ignore this flag, or as +an optimization it may return just a single extent for C<offset>. + +If there is an error, C<.extents> should call C<nbdkit_error> with an +error message, and C<nbdkit_set_error> to record an appropriate error +(unless C<errno> is sufficient), then return C<-1>. + +=head3 Extents map + +The plugin C<extents> callback is passed an opaque pointer C<struct +nbdkit_extents_map *extents_map>. This structure represents a list of +L<filesystem extents|https://en.wikipedia.org/wiki/Extent_(file_systems)> +describing which areas of the disk are allocated, which are sparse +(“holes”), and, if supported, which are zeroes. Initially the map +describes a single allocated data extent covering the entire virtual +disk. + +The C<extents> callback has to fill in any holes or zeroes areas by +calling C<nbdkit_extent*> functions, to describe all extents +overlapping the range C<[offset...offset+count-1]>. (nbdkit will +ignore extents outside this range so plugins may, if it is easier to +implement, return all extent information for the whole disk.) + +The following functions are available for plugins or filters to call: + + int nbdkit_extent_add (struct nbdkit_extents_map *extents_map, + uint64_t offset, uint64_t length, uint32_t type); + +Add an extent covering C<[offset...offset+length-1]> of one of +the following four types: + +=over 4 + +=item C<type = 0> + +A normal, allocated data extent. + +=item C<type = NBDKIT_EXTENT_HOLE|NBDKIT_EXTENT_ZERO> + +An unallocated extent, a.k.a. a “hole”, which reads back as zeroes. +This is the normal type of hole applicable to most disks. + +=item C<type = NBDKIT_EXTENT_ZERO> + +An allocated extent which is known to contain only zeroes. + +=item C<type = NBDKIT_EXTENT_HOLE> + +An unallocated extent (hole) which does not read back as zeroes. Note +this should only be used in specialized circumstances such as when +writing a plugin for (or to emulate) certain SCSI drives which do not +guarantee that trimmed blocks read back as zeroes. + +=back + +If the new extent overlaps some previous extent in the map then the +overlapping part(s) are overwritten with the new type. Adjacent +extents of the same type may also be coalesced. Thus you shouldn't +assume that C<nbdkit_extent_add> always adds exactly one more extent +to the map. + +C<nbdkit_extent_add> returns C<0> on success or C<-1> on failure. On +failure C<nbdkit_error> and/or C<nbdkit_set_error> has already been +called. + + int nbdkit_extents_foreach ( + const struct nbdkit_extents_map *extents_map, + int (*fn) (uint64_t offset, uint64_t length, + uint32_t type, void *opaque), + void *opaque); + + int nbdkit_extents_foreach_range ( + const struct nbdkit_extents_map *extents_map, + uint64_t range_offset, uint64_t range_length, + int (*fn) (uint64_t offset, uint64_t length, + uint32_t type, void *opaque), + void *opaque); + +Iterate over the extents in ascending order, calling C<fn> for each. +C<fn> should return 0 on success or -1 on failure. If a call to C<fn> +fails then C<nbdkit_extents_foreach*> also fails immediately. + +The C<nbdkit_extents_foreach_range> variant only iterates over extents +overlapping C<[range_offset...range_offset+range_length-1]>. + +C<nbdkit_extents_foreach*> returns C<0> on success or C<-1> on failure. +However it does not call C<nbdkit_error> or C<nbdkit_set_error> - it +is expected that C<fn> will call those functions on failure. + =head1 THREADS Each nbdkit plugin must declare its thread safety model by defining diff --git a/include/nbdkit-common.h b/include/nbdkit-common.h index cb9954e..860a7c4 100644 --- a/include/nbdkit-common.h +++ b/include/nbdkit-common.h @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2013-2018 Red Hat Inc. + * Copyright (C) 2013-2019 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without @@ -60,11 +60,15 @@ extern "C" { #define NBDKIT_FLAG_MAY_TRIM (1<<0) /* Maps to !NBD_CMD_FLAG_NO_HOLE */ #define NBDKIT_FLAG_FUA (1<<1) /* Maps to NBD_CMD_FLAG_FUA */ +#define NBDKIT_FLAG_REQ_ONE (1<<2) /* Maps to NBD_CMD_FLAG_REQ_ONE */ #define NBDKIT_FUA_NONE 0 #define NBDKIT_FUA_EMULATE 1 #define NBDKIT_FUA_NATIVE 2 +#define NBDKIT_EXTENT_HOLE (1<<0) /* Same as NBD_STATE_HOLE */ +#define NBDKIT_EXTENT_ZERO (1<<1) /* Same as NBD_STATE_ZERO */ + extern void nbdkit_error (const char *msg, ...) ATTRIBUTE_FORMAT_PRINTF (1, 2); extern void nbdkit_verror (const char *msg, va_list args); extern void nbdkit_debug (const char *msg, ...) ATTRIBUTE_FORMAT_PRINTF (1, 2); @@ -76,6 +80,20 @@ extern int nbdkit_parse_bool (const char *str); extern int nbdkit_read_password (const char *value, char **password); extern char *nbdkit_realpath (const char *path); +struct nbdkit_extents_map; +extern int nbdkit_extent_add (struct nbdkit_extents_map *, + uint64_t offset, uint64_t length, uint32_t type); +extern int nbdkit_extents_foreach (const struct nbdkit_extents_map *, + int (*fn) (uint64_t offset, uint64_t length, + uint32_t type, void *opaque), + void *opaque); +extern int nbdkit_extents_foreach_range (const struct nbdkit_extents_map *, + uint64_t range_offset, + uint64_t range_length, + int (*fn) (uint64_t offset, uint64_t length, + uint32_t type, void *opaque), + void *opaque); + /* A static non-NULL pointer which can be used when you don't need a * per-connection handle. */ diff --git a/include/nbdkit-filter.h b/include/nbdkit-filter.h index 71c06c8..689f209 100644 --- a/include/nbdkit-filter.h +++ b/include/nbdkit-filter.h @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2013-2018 Red Hat Inc. + * Copyright (C) 2013-2019 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without @@ -44,6 +44,9 @@ extern "C" { #define NBDKIT_FILTER_API_VERSION 2 +extern struct nbdkit_extents_map *nbdkit_extents_new (void); +extern void nbdkit_extents_free (struct nbdkit_extents_map *); + typedef int nbdkit_next_config (void *nxdata, const char *key, const char *value); typedef int nbdkit_next_config_complete (void *nxdata); @@ -58,6 +61,7 @@ struct nbdkit_next_ops { int (*is_rotational) (void *nxdata); int (*can_trim) (void *nxdata); int (*can_zero) (void *nxdata); + int (*can_extents) (void *nxdata); int (*can_fua) (void *nxdata); int (*can_multi_conn) (void *nxdata); @@ -71,6 +75,9 @@ struct nbdkit_next_ops { int *err); int (*zero) (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags, int *err); + int (*extents) (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map, + int *err); }; struct nbdkit_filter { @@ -120,6 +127,8 @@ struct nbdkit_filter { void *handle); int (*can_zero) (struct nbdkit_next_ops *next_ops, void *nxdata, void *handle); + int (*can_extents) (struct nbdkit_next_ops *next_ops, void *nxdata, + void *handle); int (*can_fua) (struct nbdkit_next_ops *next_ops, void *nxdata, void *handle); int (*can_multi_conn) (struct nbdkit_next_ops *next_ops, void *nxdata, @@ -140,6 +149,10 @@ struct nbdkit_filter { int (*zero) (struct nbdkit_next_ops *next_ops, void *nxdata, void *handle, uint32_t count, uint64_t offset, uint32_t flags, int *err); + int (*extents) (struct nbdkit_next_ops *next_ops, void *nxdata, + void *handle, uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map, + int *err); }; #define NBDKIT_REGISTER_FILTER(filter) \ diff --git a/include/nbdkit-plugin.h b/include/nbdkit-plugin.h index d43b2f5..76cec54 100644 --- a/include/nbdkit-plugin.h +++ b/include/nbdkit-plugin.h @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2013-2018 Red Hat Inc. + * Copyright (C) 2013-2019 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without @@ -125,6 +125,10 @@ struct nbdkit_plugin { const char *magic_config_key; int (*can_multi_conn) (void *handle); + + int (*can_extents) (void *handle); + int (*extents) (void *handle, uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map); }; extern void nbdkit_set_error (int err); diff --git a/server/internal.h b/server/internal.h index 506882b..e05e5b5 100644 --- a/server/internal.h +++ b/server/internal.h @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2013-2018 Red Hat Inc. + * Copyright (C) 2013-2019 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without @@ -235,6 +235,7 @@ struct backend { int (*is_rotational) (struct backend *, struct connection *conn); int (*can_trim) (struct backend *, struct connection *conn); int (*can_zero) (struct backend *, struct connection *conn); + int (*can_extents) (struct backend *, struct connection *conn); int (*can_fua) (struct backend *, struct connection *conn); int (*can_multi_conn) (struct backend *, struct connection *conn); @@ -248,6 +249,10 @@ struct backend { uint64_t offset, uint32_t flags, int *err); int (*zero) (struct backend *, struct connection *conn, uint32_t count, uint64_t offset, uint32_t flags, int *err); + int (*extents) (struct backend *, struct connection *conn, uint32_t count, + uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map, + int *err); }; /* plugins.c */ diff --git a/server/extents.c b/server/extents.c new file mode 100644 index 0000000..4b257db --- /dev/null +++ b/server/extents.c @@ -0,0 +1,71 @@ +/* nbdkit + * Copyright (C) 2019 Red Hat Inc. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * * Neither the name of Red Hat nor the names of its contributors may be + * used to endorse or promote products derived from this software without + * specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A + * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#include <config.h> + +#include <stdio.h> +#include <stdlib.h> +#include <stdint.h> +#include <string.h> +#include <inttypes.h> +#include <assert.h> + +#include "internal.h" + +struct nbdkit_extents_map { + // TBD XXX +}; + +#if 0 +struct nbdkit_extents_map *nbdkit_extents_new (void); +void nbdkit_extents_free (struct nbdkit_extents_map *); +#endif + +int nbdkit_extent_add (struct nbdkit_extents_map *extents_map, + uint64_t offset, uint64_t length, uint32_t type) +{ + // XXX + return 0; +} + +#if 0 +int nbdkit_extents_foreach (const struct nbdkit_extents_map *, + int (*fn) (uint64_t offset, uint64_t length, + uint32_t type, void *opaque), + void *opaque); +int nbdkit_extents_foreach_range (const struct nbdkit_extents_map *, + uint64_t range_offset, uint64_t range_length, + int (*fn) (uint64_t offset, uint64_t length, + uint32_t type, void *opaque), + void *opaque); +#endif diff --git a/server/filters.c b/server/filters.c index 5b7abc4..e284080 100644 --- a/server/filters.c +++ b/server/filters.c @@ -309,6 +309,13 @@ next_can_zero (void *nxdata) return b_conn->b->can_zero (b_conn->b, b_conn->conn); } +static int +next_can_extents (void *nxdata) +{ + struct b_conn *b_conn = nxdata; + return b_conn->b->can_extents (b_conn->b, b_conn->conn); +} + static int next_can_fua (void *nxdata) { @@ -364,6 +371,16 @@ next_zero (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags, return b_conn->b->zero (b_conn->b, b_conn->conn, count, offset, flags, err); } +static int +next_extents (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map, + int *err) +{ + struct b_conn *b_conn = nxdata; + return b_conn->b->extents (b_conn->b, b_conn->conn, count, offset, flags, + extents_map, err); +} + static struct nbdkit_next_ops next_ops = { .get_size = next_get_size, .can_write = next_can_write, @@ -371,6 +388,7 @@ static struct nbdkit_next_ops next_ops = { .is_rotational = next_is_rotational, .can_trim = next_can_trim, .can_zero = next_can_zero, + .can_extents = next_can_extents, .can_fua = next_can_fua, .can_multi_conn = next_can_multi_conn, .pread = next_pread, @@ -378,6 +396,7 @@ static struct nbdkit_next_ops next_ops = { .flush = next_flush, .trim = next_trim, .zero = next_zero, + .extents = next_extents, }; static int @@ -511,6 +530,21 @@ filter_can_zero (struct backend *b, struct connection *conn) return f->backend.next->can_zero (f->backend.next, conn); } +static int +filter_can_extents (struct backend *b, struct connection *conn) +{ + struct backend_filter *f = container_of (b, struct backend_filter, backend); + void *handle = connection_get_handle (conn, f->backend.i); + struct b_conn nxdata = { .b = f->backend.next, .conn = conn }; + + debug ("%s: can_extents", f->name); + + if (f->filter.can_extents) + return f->filter.can_extents (&next_ops, &nxdata, handle); + else + return f->backend.next->can_extents (f->backend.next, conn); +} + static int filter_can_fua (struct backend *b, struct connection *conn) { @@ -646,6 +680,31 @@ filter_zero (struct backend *b, struct connection *conn, count, offset, flags, err); } +static int +filter_extents (struct backend *b, struct connection *conn, + uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map, + int *err) +{ + struct backend_filter *f = container_of (b, struct backend_filter, backend); + void *handle = connection_get_handle (conn, f->backend.i); + struct b_conn nxdata = { .b = f->backend.next, .conn = conn }; + + assert (!(flags & ~NBDKIT_FLAG_REQ_ONE)); + + debug ("%s: extents count=%" PRIu32 " offset=%" PRIu64 " flags=0x%" PRIx32, + f->name, count, offset, flags); + + if (f->filter.extents) + return f->filter.extents (&next_ops, &nxdata, handle, + count, offset, flags, + extents_map, err); + else + return f->backend.next->extents (f->backend.next, conn, + count, offset, flags, + extents_map, err); +} + static struct backend filter_functions = { .free = filter_free, .thread_model = filter_thread_model, @@ -667,6 +726,7 @@ static struct backend filter_functions = { .is_rotational = filter_is_rotational, .can_trim = filter_can_trim, .can_zero = filter_can_zero, + .can_extents = filter_can_extents, .can_fua = filter_can_fua, .can_multi_conn = filter_can_multi_conn, .pread = filter_pread, @@ -674,6 +734,7 @@ static struct backend filter_functions = { .flush = filter_flush, .trim = filter_trim, .zero = filter_zero, + .extents = filter_extents, }; /* Register and load a filter. */ diff --git a/server/plugins.c b/server/plugins.c index 28b96ad..1882b00 100644 --- a/server/plugins.c +++ b/server/plugins.c @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2013-2018 Red Hat Inc. + * Copyright (C) 2013-2019 Red Hat Inc. * All rights reserved. * * Redistribution and use in source and binary forms, with or without @@ -199,6 +199,8 @@ plugin_dump_fields (struct backend *b) HAS (trim); HAS (zero); HAS (can_multi_conn); + HAS (can_extents); + HAS (extents); #undef HAS /* Custom fields. */ @@ -392,6 +394,21 @@ plugin_can_zero (struct backend *b, struct connection *conn) return plugin_can_write (b, conn); } +static int +plugin_can_extents (struct backend *b, struct connection *conn) +{ + struct backend_plugin *p = container_of (b, struct backend_plugin, backend); + + assert (connection_get_handle (conn, 0)); + + debug ("can_extents"); + + if (p->plugin.can_extents) + return p->plugin.can_extents (connection_get_handle (conn, 0)); + else + return p->plugin.extents != NULL; +} + static int plugin_can_fua (struct backend *b, struct connection *conn) { @@ -651,6 +668,47 @@ plugin_zero (struct backend *b, struct connection *conn, return r; } +static int +plugin_extents (struct backend *b, struct connection *conn, + uint32_t count, uint64_t offset, uint32_t flags, + struct nbdkit_extents_map *extents_map, + int *err) +{ + struct backend_plugin *p = container_of (b, struct backend_plugin, backend); + bool req_one = flags & NBDKIT_FLAG_REQ_ONE; + int r; + int can_extents = 0; /* XXX probably should be cached per connection */ + + assert (connection_get_handle (conn, 0)); + assert (!(flags & ~NBDKIT_FLAG_REQ_ONE)); + + debug ("extents count=%" PRIu32 " offset=%" PRIu64 " req_one=%d", + count, offset, req_one); + + if (!count) + return 0; + + if (p->plugin.can_extents) { + can_extents = p->plugin.can_extents (connection_get_handle (conn, 0)); + if (can_extents == -1) { + *err = get_error (p); + return -1; + } + } + + if (can_extents) { + r = p->plugin.extents (connection_get_handle (conn, 0), count, offset, + flags, extents_map); + if (r == -1) + *err = get_error (p); + return r; + } + else { + /* By default we assume that everything in the range is allocated. */ + return nbdkit_extent_add (extents_map, offset, count, 0); + } +} + static struct backend plugin_functions = { .free = plugin_free, .thread_model = plugin_thread_model, @@ -672,6 +730,7 @@ static struct backend plugin_functions = { .is_rotational = plugin_is_rotational, .can_trim = plugin_can_trim, .can_zero = plugin_can_zero, + .can_extents = plugin_can_extents, .can_fua = plugin_can_fua, .can_multi_conn = plugin_can_multi_conn, .pread = plugin_pread, @@ -679,6 +738,7 @@ static struct backend plugin_functions = { .flush = plugin_flush, .trim = plugin_trim, .zero = plugin_zero, + .extents = plugin_extents, }; /* Register and load a plugin. */ diff --git a/server/Makefile.am b/server/Makefile.am index b198afb..1c2fe06 100644 --- a/server/Makefile.am +++ b/server/Makefile.am @@ -43,6 +43,7 @@ nbdkit_SOURCES = \ connections.c \ crypto.c \ debug.c \ + extents.c \ filters.c \ internal.h \ locks.c \ -- 2.20.1